Leaching (metallurgy)

Compared to pyrometallurgy, leaching is easier to perform, requires less energy and is potentially less harmful as no gaseous pollution occurs.

[1] Heap leaching dates back to the second century BC in China, where iron was combined with copper sulfate.

[4] In the eighth century, Jabir Ibn Hayyan, a Persian alchemist, discovered a substance he coined "aqua regia".

[4][3] The pyrite would be set outside for months at a time, where rain and air exposure would lead to chemical weathering.

[4] Heap leaching, in this natural chemical-free form, was further developed to obtain different, more economically viable, types of ore.

[4] Potash was most frequently made from the ash remains of wood-burning stoves and fireplaces, which were agitated with water and filtered.

[4] In 1858 Adolf Von Patera, a metallurgist in Austria, utilized lixiviation separate soluble and insoluble compounds from silver in an aqueous solution.

[8] Additionally, with Patera's process, if the sodium hyposulphite failed to dissolve perfectly, silver would often be caught in the extra solution and not properly extracted.

[4] Particularly at the Mines Branch in Ottawa (now known as CANMET), it was demonstrated that pyrrhotite-penthandite concentrate could be treated in autoclaves, with the resulting nickel in a solution while iron oxide and sulfur remain in the residue.